1. Field
Exemplary embodiments of the present invention relates to a semiconductor design technology, and more particularly, to a differential amplifier.
2. Description of the Related Art
Generally, an internal voltage generation circuit for generating internal voltage is mounted in a semiconductor device including, for example, a double data rate synchronous DRAM (DDR SDRAM) and the semiconductor device may use various voltage levels of the internal voltage generated therein to secure more efficient power consumption and a more stable circuit operation. As the internal voltage, there are an internal voltage generated by down-converting supply power voltage supplied from the outside and an internal voltage generated by pumping supply power voltage and ground power voltage. Herein, the internal voltage generated by a down converting operation may include core voltage used as a data level and precharge voltage used at the time of a precharge operation, and the internal voltage generated by a pumping operation may include pumping voltage applied to a gate of a cell transistor and substrate bias voltage applied to a substrate of the cell transistor.
An internal voltage generation circuit generally performs a comparison operation of comparing an internal voltage outputted therefrom with reference voltage to determine whether the internal voltage driving operation is performed or not. Therefore, the internal voltage generation circuit includes a component for comparing internal voltage with reference voltage and the component may be a voltage detection circuit. Herein, the voltage detection circuit is generally configured as a differential amplifier.
FIG. 1 is a block diagram for illustrating a general internal voltage generation circuit.
Referring to FIG. 1, the internal voltage generation circuit includes a voltage detection unit 110 and an internal voltage generation unit 120.
The voltage detection unit 110 detects internal voltage V_INN based on reference voltage V_REF to generate an oscillation activation signal EN_OSC corresponding to a voltage level difference between the reference voltage V_REF and the internal voltage V_INN. Herein, the reference voltage V_REF may have a constant voltage level independent from temperature, that is, a voltage level is independent from the temperature.
The internal voltage generation unit 120 generates the internal voltage V_INN in response to the oscillation activation signal EN_OSC and includes an oscillator 121 and a pump 122. Herein, the oscillator 121 generates the oscillation signal OSC in response to the oscillation activation signal EN_OSC and the pump 122 generates the internal voltage V_INN by the pumping operation in response to the oscillation signal OSC. The generated internal voltage V_INN is fed back to the voltage detection unit 110 so as to be compared with the reference voltage V_REF again.
FIG. 2 is a circuit diagram for illustrating the voltage detection unit 110 of FIG. 1.
Referring to FIG. 2, the voltage detection unit 110 includes a current driving unit 210, a signal input unit 220, a current sinking unit 230, and a signal output unit 240.
The current driving unit 210 drives an output terminal and includes first and second PMOS transistors PM1 and PM2. The signal input unit 220 receives the internal voltage V_INN and the reference voltage V_REF and includes first and second NMOS transistors NM1 and NM2. The current sinking unit 230 sinks driving current flowing through the voltage detection unit 110 in response to bias voltage V_BIA and includes a third NMOS transistor NM3. In addition, the signal output unit 240 generates the oscillation activation signal EN_OSC in response to the driving current flowing through an output terminal and includes an inverter INV.
Meanwhile, as described above, the reference voltage V_REF is a signal having a constant voltage level independent from the temperature. The voltage detection unit 110 may perform a constant comparison operation based on the reference voltage V_REF, which is independent from the temperature.
However, with the recent development of a process technology, a design-rule of a sub-micron or less is applied in designing a circuit, such that a unique characteristic of a circuit may be changed according to a change in temperature. For example, in the case of the MOS transistor, according to the change of temperature, not only the threshold voltage but the characteristics of the leakage current may be changed. Therefore, the unique characteristics of the MOS transistor included in the voltage detection unit 110 of FIG. 2 may be also changed according to the temperature to cause malfunction.